A cleaning tool that uses a fluidic oscillator to create pressure fluctuations in the well bore adjacent a perforated interval to clean the perforations has been proposed. See SPE Paper No. 13803 entitled "Pressure Fluctuating Tool" by Payne, Williams, Petty and Bailey. The pulses from a fluidic oscillator are fed to respective fluid-filled chambers that are communicated by an inertia tube. Oscillating or fluctuating pressures are created in the annular space between the tool and the casing wall. Acoustic filters in the form of gas-filled rubber bladders are positioned in the tool above and below the primary oscillation zone to limit the propagation of the acoustic signals up and down the well bore, and to concentrate the pressure fluctuations to an adjacent interval of the perforations. The pressure fluctuations are said to remove debris from the perforations and pulverize any impermeable skin on the wall of the perforation tunnel, which can be caused by current methods of shaped charge perforating. Oil production from the perforations is thereby increased, and the ability to stimulate the formation using various techniques is enhanced.
However, the combination of components used in this device, particularly the elastomer bladder filters, provides a tool that is very long, in the order of 30 feet. Such a lengthy tool is quite cumbersome to handle and requires a large vehicle to transport it to and from a job site. The tool also has an outer diameter such that it can be operated only in well casings having a fairly large size which is above a size that is commonly found in many oil producing areas. Moreover, the use of acoustic filters that are placed at fixed distance above and below the resonance zone can have less than optimum performance due to inability to adjust or fine-tune the system.
The general object of the present invention is to provide a new and improved perforation cleaning tool that obviates the foregoing problems.
Another object of the present invention is to provide a new and improved tool of the type described having relatively short comments that can be transported in a car trunk or in any small, truck-type vehicle.
Another object of the present invention is to provide a new and improved tool of the type described that can be used in 41/2" as well as large size casing.
Still another object of the present invention is to provide a new and improved tool of the type described that includes an acoustic filter system that can be adjusted to fine-tune or calibrate the tool for maximum efficiency.